Memory may include one-time programmable memory cells for use for various purposes. In one example conventional memory arrangement, one memory structure is provided for writing/reading data while a separate memory structure is provided for one-time programmable cells. One-time programmable cells may be programmed by a manufacturer of the memory or perhaps an end user customer who incorporates the memory into an end product. The one-time programmable cells are written to once and may be implemented as non-volatile memory, such as fuses or anti-fuses, to permanently store the one-time programmable data.
However, it has been recognized that one-time programmable data may be undesirably changed, reversed or un-programmed from its originally programmed state under some conditions. A charge retaining region of a flash memory cell utilized as a one-time programmable cell may gain or lose charge over time to an extent that the state of the flash memory cell is indeterminate or different than the originally-programmed state. The data level of a programmed cell may approach the read level of the cell to such an extent that the state of the memory cell may be indeterminate or incorrectly determined with respect to its originally programmed state.
At least some embodiments described below are directed towards methods and apparatus which provide increased data reliability and retention of data which is programmed once compared with some conventional memory arrangements.